1. Field of Technology
The present invention relates to a vacuum insulating switch gear which is miniaturized and lightened and has high performance and reliability.
2. Description of Related Art
In recent power receiving and transformation facility, the users' demands are diversified. For example, the load kind and operation condition depend upon the use purpose, so that in consideration of the requested safety, reliability, and operation maintenance and a future increase in the load, a power distribution system is planned. However, in the power distribution system plan, the control for the circuit breaker, the disconnecting switch, and the earthing switch composing the power receiving and transformation facility and the monitoring and measurement of the voltage, current, and power of the power receiving and transformation facility must be taken into account.
In this case, it is one of the problems how to minimize the installation space of the devices of the circuit breaker, disconnecting switch, and earthing switch, the controllers, and the monitoring and measuring instruments therefore, thereby suppressing the investment in the installation. To solve the problem, a vacuum insulating switch gear including a vacuum double-break three-position type switch having a breaking-disconnecting function is proposed.
In the vacuum insulating switch gear, the vacuum double-break three-position type switch and the earthing switch with a vacuum closed container are respectively stored in a vacuum container formed by a ceramic material or a metallic material and the vacuum containers and conductors are molded integrally with epoxy resin which is used as an insulating skin, thus a switching portion is unitized, miniaturized, and lightened.
On the other hand, in such switching portion, there is a great difference in the thermal expansion coefficient between the epoxy resin and the ceramic material, so that separation of the epoxy resin cast portion and generation of cracks due to thermal stress owing to temperature changes are supposed. If the epoxy resin is cracked, the insulation property is lowered and a fault such as generation of a corona discharge is caused, thus the reliability of the vacuum insulating switch gear is extremely reduced. Therefore, it is known to coat plastic resin such as silicone rubber in the gap between a required portion of the vacuum container easily cracked due to thermal stress and the epoxy resin cast portion for the purpose of easing the thermal stress and form a stress easing layer (for example, refer to Patent Document 1).
Patent Document 1: Japanese Patent Laid-open No. 2002-358861